Copper(I) Iodide-Catalyzed Cycloadditions of (1Z,4R*,5R*)-4-Benzamido-5-phenylpyrazolidin-3-on-1-azomethine Imines to Ethyl Propiolate

Regioselective copper(i) iodide-catalyzed cycloadditions of chiral pyrazolidin-3-on-1-azomethine imines 3a j to ethyl propiolate 4 gave cycloadducts 5a-h and 5'i and 5/5'j as single regioisomers. In terms of facial selectivity, cycloadducts 5a-h and 5'i were obtained as single diastereomers, whereas the reaction of dipole 3j was less selective and gave a mixture of 5j and 5'j in a ratio of 15:85. Stereoselectivity of copper(I) iodide-catalyzed cycloadditions of ethyl propiolate 4 to azomethine imines 3 was controlled by the stereodirecting phenyl group at position 5 and by the ortho-substituents at the 1'-Ar residue.